In 2010, the U.S. Chemical Safety Board launched an investigation after a steel hose carrying phosgene gas burst at DuPont’s plant in Belle, West Virginia, killing one worker. The CSB again sent investigators out to the company’s Buffalo, New York, facility after a welder was killed in an explosion later that year.

The board began its third investigation into the company after tragedy again struck at a DuPont facility on November 15, 2014, this time inside a pesticide manufacturing unit at the company’s La Porte Plant. According to federal investigators, more than 20,000 pounds of methyl mercaptan — which, even in small doses, can attack the nervous system and trigger death by respiratory paralysis — unexpectedly spewed into the third floor of the plant’s pesticide unit when veteran operator Crystal Rae Wise opened a faulty valve on her early morning shift. Wise and the three men who rushed in to help her and other workers — Wade Baker and brothers Robert and Gilbert Tisnado — also died from the toxic fumes.

Federal regulators and investigators have asked two fundamental questions in the wake of the La Porte tragedy: What could have been done to prevent it, and is DuPont to blame for what happened? The answer to that first question has been, essentially, a great many things. To that second question, the feds have emphatically said yes, that across-the-board failures by DuPont created a hazardous environment at the La Porte plant that endangered not only the company’s workers but also the public.

Earlier this year, the Occupational Safety and Health Administration unequivocally blamed the four deaths on DuPont’s failure to fix persistent problems at the La Porte Plant. OSHA then fined the company about as much as it can under federal law: For more than a dozen willful, repeat or serious violations at the La Porte plant, OSHA has fined DuPont about $370,000, pocket change for a company that posted $35.7 billion in revenue in 2013.

Aside from that — unless congressional reforms give regulators some teeth or Texas lawmakers roll back legislation that limits what companies like DuPont have to pay out in civil lawsuits — there’s really not much else authorities can do (short of criminal action, which is almost unheard-of in such cases).

Except for loudly and publicly excoriating DuPont for its failures, that is.

The Chemical Safety Board’s interim recommendations for DuPont, released this week and approved by the board Wednesday, contain more than just measures of corrective action the board is urging DuPont to take before it resumes operations at the La Porte pesticide unit. According to CSB investigators, top-down failures at the company led to the toxic gas leak that killed four workers.

The board hasn’t only released a 48-page report on what it’s uncovered so far in its investigation. Along with taking its message to the media (see the op-ed board chair Vanessa Allen Sutherland wrote in the Houston Chronicle this week), the board has even created its own media. In a video posted to YouTube that looks more like a PBS Frontline short than a government PSA, the board explains in clear detail exactly what went wrong at the La Porte plant that day and how the tragedy could have been averted.

Perhaps the CSB’s full-court press is in part due to the fact that the findings of its investigation so flatly refute DuPont’s longstanding claims that November’s tragedy can be blamed on operator error. The CSB investigators found that many of the systems that should have been in place to prevent such accidents were not, and that some of the safety precautions and systems that were in place were defective and never replaced, fixed or even tested for their effectiveness.

For instance, OSHA chastised DuPont because ventilation fans inside the unit where the four workers died had been inoperable for months leading up to the accident, yet the company had failed to provide even basic safety training to its workers. According to the CSB report, workers on the unit even grew accustomed to the stink of low levels of methyl mercaptan. As for whether there were any monitors on the unit to detect high levels of the toxic chemical, which is deadly in even small concentrations, the CSB investigators wrote, “multiple DuPont employees informed the CSB that odor was the primary method used to locate a methyl mercaptan leak.”

Still, even if those fans had been working, investigators say they doubt the ventilation in the building could have purged the unit of toxic air in time to save those workers. At the board’s meeting at the Hilton Americas downtown Wednesday night, CSB investigator Tamara Qureshi showed a video investigators shot inside the pesticide unit while the fans were in operation. The video shows a hazy cloud, presumably chemical fumes, lingering underneath a lightbulb even as the fans rumble.

“This is not good ventilation, even when the fan is in operation,” she said. CSB investigators say their own evaluation of the system, which was never fully tested by DuPont to make sure it worked properly, indicates that the workers would have died from the toxic fumes even if the fans were up and running.

Meanwhile, investigators found other hazards at the facility that, while unrelated to November’s deadly leak, put workers and the public in danger. CSB investigator Steve Cutchen pointed to huge methyl mercaptan storage tanks on site that he says lack proper insulation and relief valve systems. “Workers and the public have been exposed to unacceptable risks” because of those tanks, he said.

While CSB investigators say DuPont officials have agreed to cooperate and implement the boards recommendations (in a statement to media this week, the company still says it “respectfully disagrees with aspects of the report and some of CSB’s findings”), that wasn’t always the case.

In fact, the CSB’s recommendations to DuPont are labeled “interim” because its investigation into the company was abruptly stalled this summer when the board learned of DuPont’s plans to restart the La Porte pesticide unit as early as this past August. Investigators say they rushed to draft their recommendations for essential systems and fixes that needed to be in place before the plant could start up again — recommendations investigators say the company refused to consider up until recently.

CSB investigators say they're not done looking into the La Porte accident, and that they plan to evaluate a number of factors that might have contributed to the tragedy — including a lax safety culture at the company. The board’s lead investigator, Dan Tillema, said he’s already heard from DuPont workers who claim the company has a habit of punishing or blaming individual workers while failing to address systemic flaws. “More of a focus on blame, less a focus on preventative corrections,” Tillema said Wednesday.

At Wednesday’s meeting, attorneys representing the families of those who died in November’s gas leak urged the board to pressure DuPont in any way it can — from championing regulatory reforms at the federal level to loudly declaring DuPont’s failures at the La Porte plant and continuing to investigate the incident.

“We have very little that we can do,” said Larry Wilson, who’s representing the Tisnado family. The Texas Legislature, he said, has set strict limits on how much can be recovered in civil lawsuits like the one his clients have filed against DuPont. “That means largely if there’s going to be change by DuPont, it rests with you all," Wilson told the board. "I hope you realize that.”